You can get an indoor antenna at Radio Shack. Note that labeling it HDTV is marketing hype that confuses the jobs of antenna and tuner. Ditto for “digital.” Antenna design is dictated by the carrier frequencies, which have never changed for broadcast tv. You can still use rabbit-ears for vhf channels 2–13 (including fm radio between ch. 6 & 7) and a bowtie or loop for uhf ch. 14–83. Shaping any physical element of these antennas to resemble a satellite dish is a marketing ploy appealing modern expectations. The one at Wal-Mart is a little less gimmicky. The newer exceptions are small flat panels like this RCA one.
The monumental change in broadcast TV in the US came in 2009, when everybody switched from analog to digital. For older tv sets without digital tuners, this means adding a converter box between antenna & tv. I used two $50 coupons from the government to purchase mine.
Nowadays “watching tv” usually means connection to a service provider like cable tv or satellite dish. A co-ax cable comes into your tv room & connects to equipment that, in turn, connects to your tv.
It’s becoming increasingly common to interface the tv to a computer rather than a tuner, watching content either stored as files or streamed over the internet by a service such as Netflix. There are special-purpose computers optimized for this purpose.
We are in the midst of “convergence” of home electronics. This process will continue for decades longer & nobody knows how it will all end up.